Guard against null for objects passed by value

Fixes #1228

Signed-off-by: Dimitar Dobrev <dpldobrev@protonmail.com>

src/Generator/Generators/CLI/CLIMarshal.cs

@@ -679,6 +679,13 @@ namespace CppSharp.Generators.CLI
 
                 if (Context.Parameter.Type.IsReference())
                     VarPrefix.Write("&");
+                else
+                {
+                    Context.Before.WriteLine($"if (ReferenceEquals({Context.Parameter.Name}, nullptr))");
+                    Context.Before.WriteLineIndent(
+                        $@"throw gcnew ::System::ArgumentNullException(""{
+                            Context.Parameter.Name}"", ""Cannot be null because it is passed by value."");");
+                }
             }
 
             if (method != null

src/Generator/Generators/CSharp/CSharpMarshal.cs

@@ -701,15 +701,38 @@ namespace CppSharp.Generators.CSharp
                 @interface.IsInterface)
                 paramInstance = $"{param}.__PointerTo{@interface.OriginalClass.Name}";
             else
-                paramInstance = $@"{param}.{Helpers.InstanceIdentifier}";
+                paramInstance = $"{param}.{Helpers.InstanceIdentifier}";
-            if (type.IsAddress())
+
+            if (!type.IsAddress())
             {
+                Context.Before.WriteLine($"if (ReferenceEquals({Context.Parameter.Name}, null))");
+                Context.Before.WriteLineIndent(
+                    $@"throw new global::System.ArgumentNullException(""{
+                        Context.Parameter.Name}"", ""Cannot be null because it is passed by value."");");
+                var realClass = @class.OriginalClass ?? @class;
+                var qualifiedIdentifier = typePrinter.PrintNative(realClass);
+                Context.Return.Write($"*({qualifiedIdentifier}*) {paramInstance}");
+                return;
+            }
+
             Class decl;
             if (type.TryGetClass(out decl) && decl.IsValueType)
-                    Context.Return.Write(paramInstance);
-                else
             {
+                Context.Return.Write(paramInstance);
+                return;
+            }
+
             if (type.IsPointer())
+            {
+                if (Context.Parameter.IsIndirect)
+                {
+                    Context.Before.WriteLine($"if (ReferenceEquals({Context.Parameter.Name}, null))");
+                    Context.Before.WriteLineIndent(
+                        $@"throw new global::System.ArgumentNullException(""{
+                            Context.Parameter.Name}"", ""Cannot be null because it is passed by value."");");
+                    Context.Return.Write(paramInstance);
+                }
+                else
                 {
                     Context.Return.Write("{0}{1}",
                         method != null && method.OperatorKind == CXXOperatorKind.EqualEqual
@@ -717,30 +740,22 @@ namespace CppSharp.Generators.CSharp
                             : $"ReferenceEquals({param}, null) ? global::System.IntPtr.Zero : ",
                         paramInstance);
                 }
-                    else
+                return;
-                    {
+            }
+
             if (method == null ||
                 // redundant for comparison operators, they are handled in a special way
                 (method.OperatorKind != CXXOperatorKind.EqualEqual &&
                 method.OperatorKind != CXXOperatorKind.ExclaimEqual))
             {
-                            Context.Before.WriteLine("if (ReferenceEquals({0}, null))", param);
+                Context.Before.WriteLine($"if (ReferenceEquals({Context.Parameter.Name}, null))");
                 Context.Before.WriteLineIndent(
-                                "throw new global::System.ArgumentNullException(\"{0}\", " +
+                    $@"throw new global::System.ArgumentNullException(""{
-                                "\"Cannot be null because it is a C++ reference (&).\");",
+                        Context.Parameter.Name}"", ""Cannot be null because it is a C++ reference (&)."");",
                     param);
             }
-                        Context.Return.Write(paramInstance);
-                    }
-                }
-                return;
-            }
 
-            var realClass = @class.OriginalClass ?? @class;
+            Context.Return.Write(paramInstance);
-            var qualifiedIdentifier = typePrinter.PrintNative(realClass);
-            Context.Return.Write(
-                "ReferenceEquals({0}, null) ? new {1}() : *({1}*) {2}",
-                param, qualifiedIdentifier, paramInstance);
         }
 
         private void MarshalValueClass()

src/Generator/Passes/CheckAbiParameters.cs

@@ -81,9 +81,7 @@ namespace CppSharp.Passes
                 });
             }
 
-            foreach (var param in from p in function.Parameters
+            foreach (var param in function.Parameters.Where(p => p.IsIndirect))
-                                  where p.IsIndirect && !p.Type.Desugar().IsAddress()
-                                  select p)
             {
                 param.QualifiedType = new QualifiedType(new PointerType(param.QualifiedType));
             }

tests/CSharp/CSharp.Tests.cs

@@ -248,7 +248,7 @@ public unsafe class CSharpTests : GeneratorTestFixture
             methodsWithDefaultValues.DefaultEmptyEnum();
             methodsWithDefaultValues.DefaultRefTypeBeforeOthers();
             methodsWithDefaultValues.DefaultRefTypeAfterOthers();
-            methodsWithDefaultValues.DefaultRefTypeBeforeAndAfterOthers(0, null);
+            methodsWithDefaultValues.DefaultRefTypeBeforeAndAfterOthers();
             methodsWithDefaultValues.DefaultIntAssignedAnEnum();
             methodsWithDefaultValues.defaultRefAssignedValue();
             methodsWithDefaultValues.DefaultRefAssignedValue();

tests/Common/Common.Tests.cs

@@ -772,6 +772,12 @@ public class CommonTests : GeneratorTestFixture
         }
     }
 
+    [Test]
+    public void TestPassingNullToValue()
+    {
+        Assert.Catch<ArgumentNullException>(() => new Bar((Foo) null));
+    }
+
     [Test]
     public void TestNonTrivialDtorInvocation()
     {